SCMatrixSubblockIter (Access access)The access variable should be one of Read, Write, Accum, and None, with theSCMatrixSubblockIter:: scope operator applied. virtual void begin ()=0Start at the beginning.virtual int ready ()=0Returns nonzero if there is another block.virtual void next ()=0Proceed to the next block.virtual SCMatrixBlock * block ()=0Return the current block.Access access () const Return the type of Access allowed for these blocks.